Title page for ETD etd-04152005-104826

Remote Power Delivery for Hybrid Integrated Bio-Implantable Electrical Stimulation System

Degree

Master of Science in Electrical Engineering (M.S.E.E.)

Department

Electrical & Computer Engineering

Advisory Committee

Advisor Name

Title

Pratul K. Ajmera

Committee Chair

Ashok Srivastava

Committee Member

Jin-Woo Choi

Committee Member

Keywords

remote power delivery

bio-implantable

gastric pacer

bio-telemetry

inductively coupled

electrical stimulation system

Date of Defense

2005-04-05

Availability

unrestricted

Abstract

Bio-implantable devices such as heart pacers, gastric pacers and drug-delivery systems require power for carrying out their intended functions. These devices are usually powered through a battery implanted with the system or are wired to an external power source. In this work, a remote power delivery system (RPDS) is considered as a means to charge rechargeable batteries that power a Bio-implanted Electrical Stimulation System (BESS). A loosely coupled inductive power transmitter and receiver system has been designed to recharge batteries for a bio-implanted gastric pacer.

The transmitter coil is periodically worn around the waist. The receiver coil, rechargeable batteries, battery-charging chip and the chip containing electrical stimulation circuitry form a bio-implanted hybrid integrated microsystem. The link efficiency between a transmitter coil and the implanted receiver coil when the diameters are markedly different is analyzed. A design methodology for RPDS is proposed based on the load and voltage required at the load. An analytical model is developed with the help of simple Matlab coding. A full wave rectifier with a voltage doubler circuit is used for the conversion of ac voltage to the required dc voltage. This dc voltage supplies power to a battery charging chip which is used to safely and appropriately charge a rechargeable Li-ion battery.

For an input supply voltage of 17.67 V rms, operating frequency of 20 kHz and radial coplanar displacement between the coil axes of 7.5 inches, the maximum dc voltage and power obtained across a 65Ω load resistor are 9.65 V and 1.33 W respectively. For a radial coplanar displacement between the coil axes of 6 inches, a 3.7 V nominal, 150 mAh polymer lithium ion battery has been successfully charged in 1 hour and 40 minutes from an initial voltage of 3.39 V to 4.12 V with an input voltage of 19.81 V rms at 20 kHz.

An attempt has been made to model coil parasitics at high frequency. Variations in the load power as a function of frequency and radial coplanar displacement of the axes are examined. Design strategies to optimize power delivery with given geometric constraints are considered.